1. Field of the Invention
This invention relates to a plate clamping apparatus for leaf-type printing machines, and more particularly, to a mechanism for shifting a plate wrapped around the plate roller of a printing machine in order to adjust the position of the plate so as to eliminate shears in printing.
2. Description of the Prior Art
In a multiple color leaf-type printing machine, which prints multiple colors on a single leaf of paper, plates should be wrapped around respective plate rollers with as little shear as possible so that the positions of the patterns printed by the respective printing units coincide and precise elegant printed matter is obtained.
The plate clamping apparatus of a conventional leaf-type printing machine, for example as shown in FIGS. 1(1) and 1(2), is accommodated in a recess 29 formed in the axial direction of a plate roller P and comprises as its main component a top side plate clamp W, a bottom side plate clamp S, and a plate stretcher for stretching a plate Y wrapped around the plate roller P.
The plate Y is attached in this conventional plate clamping apparatus as follows:
First, the notches of a top side cam shaft 51 and a bottom side cam shaft 55 are directed upwardly by a tool which is suspended from tool suspenders 28a and 28b so that the tip of top side upper teeth 53 and bottom side upper teeth 57 are lifted and opened, being urged by the force of springs 36 and 37, using spherically headed bolts 25a and 25b as fulcrum. The bottom side plate clamp S is offset toward the bottom side lateral wall 56 when the notch of a plate stretching cam shaft 59 is directed to the top of respective fine adjustment bolts 52e, 62f, 62g, and 62h since the tops of the fine adjustment bolts 62e, 62f, 62g, and 62h are pressed against the plate stretching cam shaft 59. Next, the plate roller P is rotated to a position at which the top end of the plate Y can be readily inserted between the top side upper teeth 53 and top side lower teeth 54 of the top side plate clamp W. The top side cam shaft 51 is then rotated by manual operation to close the top side upper teeth 53 to thereby clamp the top end of the plate Y. When the clamping of the top end of the plate Y by the top side plate clamp W is completed, the plate roller P is rotated, with the plate Y closely contacting the peripheral surface of the plate roller P, to a position where the bottom end of the plate Y can be easily attached to the bottom side plate clamp S. At this position, the bottom end of the plate Y is inserted between the bottom side upper teeth 57 and bottom side lower teeth 58. The bottom side cam shaft 55 is then rotated by manual operation to close the bottom side upper teeth 57 and accordingly clamp the bottom end of the plate Y. Next, the plate stretching cam shaft 59 is rotated by a tool, which is suspended from the tool suspender 28c at the end of the cam shaft 59, and the bottom side clamp S is moved away from the bottom side lateral wall 56. As a result, the plate Y is stretched to closely contact the peripheral surface of the plate roller P. Incidentally, removal of the plate Y is achieved by reversing the above-mentioned procedure.
With the plate Y thus wrapped around the plate roller P, a trial printing is performed to examine for shears in the respective colors. A shear in the vertical direction, i.e. in the direction which the paper is transported, is eliminated by adjusting respective fine adjustment bolts 62a, 62b, 62c, 62d, 62e, 62f, 62g, and 62h. A shear in the horizontal direction, i.e. the direction perpendicular to the paper transporting direction, is eliminated by rotating adjusting bolts 61a, 61b, 61c, and 61d for the top and bottom sides. Specifically, to move the top side plate clamp W toward the left as seen in FIG. 1, the adjusting bolt 61a on the top side is rotated away form the adjacent lateral wall of the plate P to form a gap between its head and the lateral wall. Nest, by rotating the adjusting bolt 61b while its head is in contact with the other lateral wall of the plate roller P, the top side plate clamp W is moved toward the left by the necessary amount. After movement by the necessary amount, the adjusting bolt 61a is rotated until its head comes into contact with the lateral wall of the plate roller P. Selective movement of the top side plate clamp W in the left or right direction is limited by the adjusting bolts 61a and 61B when the heads are in contact with one and the other lateral sides of the plate roller P.
Next, the procedure of lowering the top left side of the plate Y will be explained. First, the adjusting bolts 61a, 61b, 61c, and 61d are rotated to form a narrow gap between the head of the respective adjusting bolts and the side walls of the recess 29. Next, the fine adjustment bolts 62e, 62f, 62g, and 62h on the bottom side are rotated to bring the bottom side plate clamp S close to the bottom side lateral wall 56. As a result, the left side gap portion becomes wider while the right side gap portion becomes very narrow. Then, the fine adjustment bolts 62a, 62b, 62c, and 62d on the top side are respectively rotated such that the top side plate clamp S is moved away from the top side lateral wall 52, whereby the left side gap becomes wider while the right side gap becomes very narrow. In other words, the fine adjustment bolts are rotated in a manner that the top side plate clamp W is moved by the amount by which the bottom side plate clamp S was brought close to the bottom side lateral wall 56, thereby making it possible to shift the plate Y for adjustment. When the plate Y has been shifted as mentioned above, the fine adjustment bolts 62a, 62b, 62c, and 62d are rotated in the opposite direction to bring the heads of the respective fine adjustment bolts into contact with the side wall of the recess 29 to limit lateral movement of the plate clamps S and W, thus, terminating a shifting procedure for the plate Y in one direction. It will be understood that a shift of the plate Y in the opposite direction can also be achieved in the same manner as explained above.
Thus, in order to adjust the position of the plate in the conventional apparatus, complicated and time-consuming manual work such as fastening and loosening multiple fine adjustment bolts with a tool is required. Also, since the adjustment procedure includes many steps, the operator must be well-experienced in the adjustment. In addition, since such work is done in a small place and at a relatively elevated position, the work cannot be completed in a short amount of time. Further, since the adjustment must be carried out by manual operation, it is not possible to provide a high working efficiency and favorable adjustment efficiency.